Mineralpedia Details for Andradite

A member of the Garnet Group named for J.B. d’Andrada e Silva, a Brazilian mineralogist who was the first to describe a variety of this type of garnet. Andradite is common and widespread, and good material can be found in Italy, Romania, Switzerland, Norway, South Africa, Russia, the United States, and Mexico. Hundreds of other localities ate known. Andradite occurs “in skarns from contact metamorphosed impure limestones or calcic igneous rocks, in chlorite schists and serpentinites, [and] in alkalic igneous rocks, [where there are] then typically titaniferous. Associated minerals include vesuvianite, chlorite, epidote, spinel, calcite, dolomite, and magnetite.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/andradite.pdf

Formula

Ca₃Fe³⁺₂(SiO₄)₃ 

Crystal System

Isometric 

Crystal Habit

Crystalline - Coarse, Euhedral Crystals, Massive 

Cleavage

None, None, None 

Luster

Vitreous (Glassy) 

Color

black, yellowish brown, red, greenish yellow, gray 

Streak

white 

Class

Isometric - Hexoctahedral 

Fracture

Conchoidal 

Hardness

6.5-7 

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Single, euhedral, reddish brown, lustrous crystals to 6mm.

Dodecahedral crystals to 4mm.

Beautiful yellow-brown Andradite variety Topazolite crystals from 2-5mm on all sides of matrix.

The varietal name refers to resemblance of these Garnets to Topaz, which indeed they do have that same nice clear color and adamantine luster.

Deep reddish brown lustrous crystals to 8mm.

Light green garnet crystals to 5mm.

Deep red well-formed garnets to nearly 2cm on quartz with many others.

Green crystals to 4mm.